Cards of modern design are generally surrounded by casings. Such a casing may be required by safety regulations. Also, such casings may be dictated by considerations relating to air purity. In order to effectively remove any fluff, trash particles or other dirt particles arising during the carding, suction means are connected to the interior of the casing to generate a pressure below atmospheric within the encased space. In this way fibrous particles, trash particles and other dirt particles are sucked away.
Presently known carding machines of this type are typified by the C4/1 offered by Maschinenfabrik Rieter and the DK740 of the Truetzschler company. In such machines, conveying air may be admitted to the interior of the card casing through one or several suction openings having a small combined suction area as compared to the total area of the casing. Such suction openings are covered by a screen grating which is partly provided with a filter cloth.
If the air streams generated in the atmosphere surrounding the casing flow with a significant velocity, they can draw dust, fly, debris and the like into the casing. If such material flows through the machine to the extractor fan of the cleaner system, no special problems arise. However, if the air streams entering the card casing are subjected to deceleration (or even sharp deviations), the air streams will tend to deposit the dust, fly, particulate material and other fiber debris which they carry into the casing. Such a depositing can occur at a position where no special cleaning system is provided. In other words, the air drawn into the casing for purposes of cleaning specific locations within the card casing actually contributes to accumulation of dirt, fly and debris at other positions within the casing.
The use of filter cloth positioned over the air inlet openings as mentioned above provides a way of addressing with this problem. However, the filter must be cleaned or replaced somewhat regularly to prevent the filter from becoming clogged and choking. If that occurs, the under-pressure in the casing draws air into the casing at any place possible--usually through cracks in the casing and thus at high flow rates. Consequently, the problem once again arises of depositing dust, fly and other particulate material at places where no special cleaning systems are provided.
Due to the large suction effect exerted in the existing machines, it is useful to seal the smaller gaps and openings which inevitably exist in connection with the casing of such a machine so as to prevent uncontrolled inflow of external air at unintended locations. To prevent such an inflow of air at unintended places, it is necessary that the best possible sealing be provided in the casing, so that external air is only sucked into the casing at the openings provided for this purpose.